Roberto Mancini took what may have been his last chance on Mario Balotellion Sunday. A last chance for both of them, perhaps. With so much at stake as Manchester City faced their local rivals, Mancini chose his 22-year-old compatriot to lead the line: a striker whose haul for the season amounted to one goal in 12 appearances.

Just over 50 minutes later, having given the performance of a man who would have had trouble leading a line-dance at Oldham Astoria, Balotelli was trotting to the touchline, exchanging salutations with Carlos Tevez and disappearing straight down the tunnel, peeling off his gloves as he went. Manchester City's fightback was about to begin.

It proved to be a stirring experience for the home fans. But it was not enough, and after Robin van Persie's stoppage-time free-kick had decisively reversed the momentum of the previous 40 minutes, it was impossible not to look back and see the selection of Balotelli as a decision that cast further doubt on Mancini's judgment.

Mancini has always believed in Balotelli, whom he brought to England two years ago, paying £24m for a 20-year-old whose off-duty escapades were already attracting more attention than his achievements on the pitch. Were he to fulfil his potential, the manager has always assured us, he would be recognised as the equal of Lionel Messi or Cristiano Ronaldo.

It was Balotelli's prodded pass that enabled Sergio Agüero to score the goal which gave City the title in May. But the only occasion on which Mancini's protege has lived up to the Messi/Ronaldo billing was in Warsaw in June, when he was wearing the blue of Italy rather than that of City while scoring the two fine goals which defeated Germany and took his country to the Euro 2012 final in Kiev in Kiev, where he was a negligible factor.

On Sundaywe saw the Balotelli of Kiev rather than Warsaw. Stuck in a familiar groove between balefulness and petulance, always looking for the instant flick rather than the sort of authoritative touch that would have announced him as a genuine presence, Balotelli betrayed his manager's faith. But City's belief in Mancini will not have been enhanced by the contribution of Tevez, who came on to provide the dynamism that the team had lacked, linking the play and having a hand in both City's goals.

The Argentinian's tally of seven goals in 17 league appearances before Sunday might have been thought to justify his inclusion from the start of this top-of-the-table battle, particularly since he would have been keen to do well against a manager who had declined to make the necessary investment in retaining his services three years ago. For a City side experiencing difficulty in finding the net, he surely represented the man most likely to deliver.

However, with the eyes of the football world on the Premier League's big pre-Christmas fixture, he was given less than half the match in which to restore his side's fortunes. For 51 minutes he was forced to sit on the sidelines and watch Balotelli go through a repertoire of largely ineffective interventions.

In the sixth minute the Italian struck a free-kick that, deflected by David Silva's heel, forced David de Gea into a scrambled save at the foot of a post. That was as good as it got.

Four minutes later he met Gaël Clichy's excellent cross, delivered from the byline after a lung-bursting run, with a negligent volley that soared into the stand. Soon he was losing the ball to Jonny Evans's simple tackle and reacting with an unpleasant foul that led to Evans's departure after half-time.

Within seconds Balotelli was losing the ball again, this time after a lovely lay-off from Agüero, and watching as United broke forward as if rebounding off a trampoline for Rooney to score his first goal.

And so it went on. A flick here, a back-heel there, but nothing to trouble United's defence, and the arrival of Tevez cast his all-round ineffectuality in an even harsher light. At last City had 11 players on the field.

Ferran Soriano and Txiki Begiristain, City's new chief executive and football director, will have taken note, and they may have been disappointed by the latest words of Silvio Berlusconi, the owner of Milan, who had been linked with a possible move for Balotelli in January.

Speaking on Saturday during a visit to Milan's training camp, the former Italian premier claimed that his earlier remarks had been misquoted. "I did not say that 'Mario would be a dream'. I do not dream about such things at night," Berlusconi said. "There has been no approach for him. He would cost too much."

Mancini accepted criticisms of Balotelli's display. "I love Mario as a guy and a player," he said, "but it is important for him to start to think about his job. He has everything [he needs] to play well, but he cannot play like he played today.

"I saw players in my life with this fantastic quality who ended up with nothing. I don't want this for him. I chose him today because he is young and he can run and could cause a big problem for their defenders. But we did not lose this game because of Mario."

Not everyone would agree with that verdict, and it remains to be seen whether the dissenters include the men now in charge of City's fortunes.